This invention relates to a nonwoven fabric making apparatus particularly to make nonwoven fabrics.
There has already been developed a nonwoven fabric making apparatus particularly to make nonwoven fabrics by continuously feeding a fibrous web on a conveyor belt moving at a predetermined velocity, ejecting streams of high pressure fluid from a plurality of nozzles against the upper surface of the web, and thereby entangling component fibers of the web together to form nonwoven fabrics.
Japanese Patent Application Disclosure No. 1994-207360 describes a nonwoven fabric making apparatus comprising a nozzle head adapted to eject streams of high pressure fluid against a fibrous web travelling in a given direction. The nozzle head is supported by a pair of oscillating bearings so that the nozzle head may be movable back and forth in its axial direction. The nozzle head may be reciprocated at uneven amplitudes transversely of the direction in which the web travels in the course of ejecting the streams of high pressure fluid.
The Japanese Patent Application Disclosure No. 1994-207360 intends to alleviate the formation of impact traces on the fiber entangled sheet.
While the Japanese Patent Application Disclosure No. 1994-207360 intends to solve this problem of impact traces by unevenly oscillating the nozzle head, a pattern is still formed by the oscillation at the uneven amplitude occurring transversely of the sheet. Consequently, the formation of bellows-like impact traces is inevitable.
Oscillation of the nozzle head at a relatively high velocity would make it impossible to focus the stream of high pressure fluid to desired spots on the web and thereby to entangle component fibers closely together.
It is an object of this invention to provide a nonwoven fabric making apparatus enabling component fibers of a web to be reliably entangled without any impact traces by streams of high pressure fluid thereon.
According to this invention, there is provided a nonwoven fabric making apparatus having a Y-axis and an X-axis intersecting the Y-axis, the apparatus comprising a plurality of nozzles adapted to eject streams of high pressure fluid against at least one surface of a fibrous web continuously traveling in a direction of the Y-axis, to entangle component fibers of the web, the nozzles being arranged at predetermined intervals in a direction of the x-axis to form a straightly extending first nozzle array declined at a predetermined angle with respect to the Y-axis.
According to one preferred embodiment of this invention, the respective nozzles of the first nozzle array are arranged at regular intervals in the direction of the X-axis and a plurality of straight lines extending parallel to the Y-axis to connect centers of corresponding nozzles in the respective nozzle arrays in alignment are successively spaced one from another by a distance P given by
P=A1 sin xcex11
in which
A1: a length of the segment extending between centers of a pair of adjacent nozzles, and
xcex11: a declination angle of the first nozzle array with respect to the Y-axis, and wherein the distance P is in a range of 0.1xcx9c0.25 mm.
According to another preferred embodiment of this invention, between the each pair of adjacent nozzles in the first nozzle array, a predetermined number (n) of nozzles are arranged at predetermined intervals in said directions of the Y-and X-axes so that the predetermined number (n) of nozzles define secondxcx9cnth nozzle arrays extending parallel to the first nozzle array in the direction of the X-axis.
According to still another embodiment of this invention, the secondxcx9cnth nozzle arrays are successively spaced from the first nozzle array and one from another and the predetermined number (n) of nozzles defining the second xcx9cnth nozzle arrays lie at positions bisecting a length between each pair of adjacent nozzles in the first nozzle array, wherein a declination angle xcex12 of the firstxcx9cnth nozzle arrays with respect to the Y-axis is given by       α    2    =                    tan                  -          1                    ⁢                        B          ⁢                      (                          n              -              1                        )                                    2          ⁢                                                    A                2                            ⁢                              (                                  n                  -                  1                                )                                      /            n                                =                  tan                  -          1                    ⁢              nB                  2          ⁢                      A            2                              
in which
xcex12: declination angle of the nozzle arrays with respect to the Y-axis,
A2: length of a segment connecting centers of each pair of adjacent nozzles in the first nozzle array,
B: distance between each pair of adjacent nozzle arrays in the direction of the Y-axis, and
n: the number of nozzle arrays arranged in the direction of the Y-axis, and wherein a distance P between each pair of adjacent the straight lines extending in parallel to the Y-axis to connect the centers of the corresponding nozzles in the respective nozzle arrays in alignment is given by   P  =            C      ⁢              xe2x80x83            ⁢      sin      ⁢              xe2x80x83            ⁢              α        2              =                            A          2                n            ⁢      sin      ⁢              xe2x80x83            ⁢              α        2            
in which
C: distance between each pair of adjacent nozzle arrays in the direction of the X-axis, and wherein the distance P is in the range of 0.1xcx9c0.25 mm. by that the nozzles are arranged at desired intervals in the direction of the X-axis to form a straightly extending first nozzle array declined at a predetermined angle with respect to the Y-axis.